Objectives: To investigate gp41 variability and correlation with viro-immunological parameters in 54 HIV-1-infected patients receiving enfuvirtide added as single active drug to a failing regimen.
Methods: One hundred and two HIV-1 gp41 sequences and clinical follow-up from 54 enfuvirtide-treated patients were analysed from baseline to week 36 of treatment. The association of mutations with viraemia/CD4 count was assessed by Mann-Whitney test.
Results: The addition of enfuvirtide to the failing regimen induced at week 4 a viraemia decrease from 5.1 to 4.3 log(10)/mL (P = 0.0002) and a CD4 increase from 48 to 106 cells/mm(3) (P = 0.008). While viraemia rebounded to 4.8 and 4.6 log(10)/mL at week 12 and 36, respectively, CD4 continued to increase to 136 cells/mm(3) at week 36. Enfuvirtide resistance mutations, rarely found at baseline, occurred in 45/54 (83.3%) enfuvirtide-treated patients. V38A/E were the most represented mutations at all time-points. The presence of V38A/E was significantly associated with a 4.5-fold CD4 increase from baseline to week 24 and with a 6-fold increase at week 36 (P = 0.004 and 0.02 compared without V38A/E, respectively), without significant correlation with viraemia. In contrast, Q40H + L45M (present in six enfuvirtide-treated patients at week 36) correlated with CD4 loss from baseline to week 36 (P = 0.02), without significant correlation with viraemia. Mutation N126K (observed in six enfuvirtide-treated patients, never found at baseline) abrogates the fourth gp41 glycosylation site and correlates with a 2.1-fold CD4 increase at week 24.
Conclusions: Specific enfuvirtide resistance mutations (V38A/E) are associated with a sustained CD4 increase, without remarkable effects upon viraemia. This CD4 recovery, due to virus- and immune-mediated mechanisms most probably not applicable to protease/reverse transcriptase inhibitors, is important for innovative therapeutic strategies.